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battery disconnect/kill switch

nickjonesn4

Well-known member
Joined
10 Aug 2017
Messages
992
Hi All,

Would like to fit one of these but have managed to get confused looking at options. Can someone recommend a simple DIY option please.

Was looking at the rennline options but not sure what parts I need

thanks in advance

Nick
 
Nick, much depends on what you want to fit the switch to and what you hope to achieve. For safety the usual is to break the main earth from the battery to the chassis.

For additional security there are switches with removable keys.

Problem for ECU controlled vehicles is that operating such switches can create ECU issues involving re learning and possible lost personal settings of some kit..

There are quite a selection of switches on the market..

https://www.demon-tweeks.com/uk/mot...protection/battery-isolators-master-switches/

Good luck in your choices.
 
The wiring of a battery isolator is different to a kill switch.
It is possible to damage the altenator if the isolator is used on the earth terminal and switched off when the engine is running.
A kill switch fits on the live side, cuts the altenator feed and diverts it to a large ceramic resistor, more complicated and reserved for motosport use.
I tried a Cartek one on the 944 but it played havoc with the immobiliser. The simple ones connected to the earth with a fused spur to keep radio and ecu live (to avoid reset) will still allow a current drain but the fuse blows if the starter is removed.
I use a motor sport one fitted as per RS, the one mentioned above is made of brittle brass and will snap off if you throw anything in the frunk.
 

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Albionmuz said:
ToreB said:
This works fine in both my 993 and VW veteran.
Be sure to not overtighten, it will break off.
Tore

https://www.biltema.no/bil---mc/elektrisk-anlegg/strombrytere/batteribryter-pa-pol-2000031707

Exactly what I use on my GTV since it started having a slow battery drain. Takes seconds to turn off and on, car is seldom used so it works well for me. Recommend it

I have one of these too. Don't use it often but nice to have the option.
 
Albionmuz said:
ToreB said:
This works fine in both my 993 and VW veteran.
Be sure to not overtighten, it will break off.
Tore

https://www.biltema.no/bil---mc/elektrisk-anlegg/strombrytere/batteribryter-pa-pol-2000031707

Exactly what I use on my GTV since it started having a slow battery drain. Takes seconds to turn off and on, car is seldom used so it works well for me. Recommend it

I have one of these too. Don't use it often but nice to have the option.
 
Great that there are a variety of switches in use and they all seem to work for the folk who fitted them...other than Endoman`s contribution where he determines that there is a good chance of damage to the alternator if the battery isolator is switched off...

The logical question would seem to be why would the switch be operated with the engine running...?

There can be a number of reasons to fit a kill switch but like most MODIFICATIONS to an ORIGINAL design it is perhaps best to accurately determine what you hope to achieve, and also more importantly to consider the possible domino effect on other aspects of the vehicles operation as the result of the mods...?

As has been mentioned in the few replies to date, there can be issues arising, perhaps not originally considered when switches were originally fitted...?

Just thinking in type.
 
thanks all, very helpful

Richbrook Discarnect ordered
 
Luddite said:
Great that there are a variety of switches in use and they all seem to work for the folk who fitted them...other than Endoman`s contribution where he determines that there is a good chance of damage to the alternator if the battery isolator is switched off...

The logical question would seem to be why would the switch be operated with the engine running...?

There can be a number of reasons to fit a kill switch but like most MODIFICATIONS to an ORIGINAL design it is perhaps best to accurately determine what you hope to achieve, and also more importantly to consider the possible domino effect on other aspects of the vehicles operation as the result of the mods...?

As has been mentioned in the few replies to date, there can be issues arising, perhaps not originally considered when switches were originally fitted...?

Just thinking in type.

That's the difference between a kill switch and an isolator. A kill switch is mandatory in motorsport, but if you use an isolator attached to the earth as a kill it will not kill the engine only the altenator. It used to work, sort of with dynamos but not immediate, the idea is to stop fuel flow in case of a prang. Some cars are fitted with a fuel flow cut off as standard when the airbags blow not sure if the 993 has one.
 
I use this on my 964 it's basic but functions fine
 

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Endoman, many thanks for the heads up on the difference betwixt a kill switch and a battery isolator.

As Nick did not provide any info on what he hoped his switch would achieve, I assumed he was perhaps into battery isolation for a road car to cut down on battery drain when not in use, as opposed to requiring to fit a kill switch to a competition vehicle that requires to comply with RAC regs..

Strange as it may seem, my old sports car has an automatic "safety" fuel pump shut off circuit, in that the supply to the fuel pump is switched through the oil pressure switch... in the case of an accident and the engine shutting down with the ign still left switched on, the oil pressure drops breaking the contacts in the oil pressure switch and killing the fuel pump and thus avoiding possibly damaged fuel line spewing fuel around the locality..

The disadvantage in the above scenario for a vehicle that may spend varying amounts of time laid-up is that fuel can evaporate or loose pressure in varying degrees, and with a battery which may be somewhat lacking relative to the time laid up, the requirement to spin the engine until oil pressure builds up enough to close the pressure switch contacts to then bring the fuel pump into operation which again will require time to restore fuel volume/pressure.... The battery may just not have enough power, to manage to complete the whole start up process..?

I note that Iain typed of the fuel pump on some Porsches being activated by operating the door handle to pre pressurise the fuel system to provide a quick start up... However if the battery is isolated, that first step in the logic would have been by-passed, and when the battery connection was finally made in the frunk, it may create a measure of confusion in the control stratedgy...?
 
nickjonesn4 said:
thanks all, very helpful

Richbrook Discarnect ordered

It can be a bit fiddly getting this onto the battery cable, if i remember correctly i had to move the battery cable to go around the side of the battery to get that little bit extra length needed to get the discarnect on.

As others have said dont overtighten the removable wheel!

I didnt bother fitting the fuse link as this allows the clock to still run, which is exactly what drains the battery.

:D
 

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